Researchers Turn Coffee Waste Into High-Performance CO2 Capture Material
Scientists have developed a method to transform discarded coffee grounds into activated carbon granules that capture carbon dioxide efficiently and inexpensively. The breakthrough could accelerate deployment of carbon capture technology by using abundant industrial waste, reducing both costs and environmental impact of CO2 removal systems.
Originaltitel: Hierarchically structured activated carbon granules for CO2 sorption via high-shear wet granulation and activation of waste coffee dust
Forskare vid Luleå tekniska universitet har utvecklat en tillverkningsmetod för aktiverat kol från kaffeböner som förbättrar CO₂-avskiljning. Genom våt granulering med höga skjuvkrafter blandar man kaffeavfall med polymärkulor och sackaros, följt av aktivering med kaliumhydroxid. Resultatet blir mekaniskt stabila granuleringskorn i 3–5 millimeters storlek med hierarkisk porstruktur. Dessa korniga material uppnår specifika ytareor på upp till 1 573 m²/g och CO₂-kapaciteter på 4,3 mmol/g vid lågt tryck respektive 10 mmol/g vid högt tryck. Selektiviteten mellan CO₂ och kväve ligger mellan 17,7 och 21,2, vilket indikerar fysisk absorption och effektiv återregenering. Metoden är skalbar utan separat pelletering och omvandlar industriavfall till högpresterande sorptionsmaterial. För företag som värderar cirkulär ekonomi och CO₂-teknik ger detta ett praktiskt alternativ till konventionella granuleringprocesser och möjlighet att reducera råvarukostnader.
<p>The processing of composite granules of waste coffee dust and hollow polymer microspheres with sucrose solution as binder with high-shear granulation is demonstrated as a precursor for subsequent conversion to highly porous, hierarchically porous, mechanically stable structured granules for CO2 capture. The optimization of the granulation parameters, such as binder volume, waste coffee dust to hollow polymer microsphere weight ratio, and the agitator & chopper speed of the granulator, produced near-spherical granules of 4–16 mm in diameter. Subsequent pre-carbonization followed by activation using KOH as a chemical activator yielded activated carbon granules (ACGs) in the 3–5 mm size range. The ACGs exhibited hierarchical porosity with a high specific surface area (350–1573 m2 g-1), total pore volume (0.14–0.54 cm3 g-1), and significant microporosity (0.08–0.50 cm3 g-1). These textural properties enabled high CO₂ adsorption capacities of up to 4.3 mmol g-1 and 10 mmol g-1 at 1 bar and 10 bar, respectively, at 20 °C. The ACGs demonstrated a CO₂/N₂ selectivity in the range of 17.7 to 21.2 and a moderate isosteric heat of adsorption (18–43 kJ mol-1), indicating physisorption and efficient regeneration potential. These findings highlight the potential of structured ACGs as a sustainable, high-performance material with ease of processing for practical CO2 capture and gas separation applications, contributing to circular economy goals through waste valorization. This work demonstrates a scalable shaping route from spent coffee waste to mechanically robust, hierarchically porous granules without a separate palletization step, suitable for practical CO2 capture applications and also contributing to circular economy goals through waste valorization.</p>